Engineering at a scale of millionths of a metre could build human organs such as livers and kidneys - and create a "smart" artificial knee which would know when it had become infected, researchers said yesterday.

A team from the Massachusetts Institute of Technology told an American Society for Microbiology conference in New York that the kind of nanotechnology used to etch the surfaces of a silicon chip could make layers of liver or kidney cells and create a network of microscopic tubes which could deliver oxygen and nutrients to them.

"Our microfabricated devices can efficiently supply oxygen and nutrients to sustain the viability of human liver and kidney cells for at least one week in the lab," Mohammad Kaazempur-Mofrad told the conference on micro, bio and nano systems.

"So far we have succeeded in making individual, functioning units but the ultimate goal is to make whole functioning organs."

Garth Ehrlich of the Allegheny Singer Research Institute in Pittsburgh told the conference that he and colleagues were working on intelligent implants that would signal to a physician when things went wrong.

"Two to three per cent of total joint replacements fail due to chronic bacterial biofilm infections," he said.

"The only recourse for such patients is the traumatic removal of the implants, which results in additional bone loss, extensive soft tissue destruction, months of forced bed rest with intravenous antibiotics and significant loss of quality of life due to complete loss of mobility."

He foresaw an intelligent implant covered with microelectronic mechanical devices which could detect infection and identify the bacteria doing the damage. The same devices could dispense antibacterial treatment from a reservoir in the hip or knee joint, and send wireless reports to the patient's doctors while they monitored the healing process.

"There are technical hurdles that still need to be overcome but I'm fairly confident that technology is evolving rapidly enough that we will be able to do this," he said. "The ever increasing number of total joint replacements now being performed on an ageing US population makes this disease a high priority for the development of new interventional strategies."